PROJECT SUMMARY/ABSTRACT Leveraging School Environments to Shape Social Networks and Prevent Substance Use?A Pilot Randomized Trial of a Social Network Intervention Despite decades of prevention work, recent data suggest that, by the end of high school, over 27% of teens regularly use marijuana and nearly 47% regularly use alcohol. Although social networks are thought to have a strong influence on adolescent substance use, few interventions target social networks to improve health behaviors. Specifically, it remains unknown whether schools might intentionally re-wire adolescent social networks to prevent or reduce substance use. Advancement via Individual Determination (AVID) is a widely disseminated college preparatory program targeting students in the academic middle (largely B and C-average students) for additional academic and emotional support. AVID removes middle-tier students from typical classrooms and groups them together with high performing students, exposing them to a peer network in which academic performance and positive social norms are valued. In addition, by strengthening the student/teacher relationship, AVID expands students' network of supportive adults. Although evaluations of AVID suggest it improves educational outcomes, particularly for boys, there are no studies investigating whether it improves health behaviors like substance use. Using a randomized controlled study design, this pilot will test whether AVID re-wires social networks and reduces substance use among high school youth, the specific aims of which are 1) to evaluate whether students randomized to AVID report healthier social networks (lower proportion of peers engaging in risky behaviors and a higher number of supportive adults) compared with control students; 2) to determine whether AVID students report decreased frequency of 30-day alcohol, marijuana and other drug use compared to control students and whether associations between AVID and substance use are modified by gender; and 3) To examine whether peer or adult social network changes predict changes in substance use and, if exposure to AVID is associated with substance use, whether these associations are mediated by changes in peer or adult networks. Students who qualify for entry into AVID will be randomized via an admissions lottery to receive an invitation into the program or not. Intervention and control students will be assessed via a computerized survey at baseline, prior to entering high school, and then annually at the end of 9th, 10th and 11th grade. Student surveys will ask about substance use behaviors and the students' personal social network, and will be matched with their academic data from the Department of Education. Information to be gained from this study can elucidate potential causal pathways linking school environments, social networks, and substance use, forming the basis for a large-scale evaluation of AVID and the development of future social network interventions. This topic is in keeping with NIDA's mission to develop and disseminate research that significantly improves prevention, treatment and policy as it relates to drug abuse and addiction.